Manufacture of multifocal ophthalmic lens molds

ABSTRACT

A method of manufacture of molds for casting finished multifocal plastic ophthalmic lenses of the type wherein the corrections for the near field of vision are provided on the convex surface of the finished lens.

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States atent Rosenbauer Mar. 14, 1972 [54] MANUFACTURE OF MULTIFOCALOPHTHALMIC LENS MOLDS References Cited [72] Inventor: Charles H.Rosenbauer, lrondequoit, N.Y. UNITED STATES PATENTS [73] Assignee:Bausch & Lomb Incorporated, Rochester, 2,049,094 7/1 NY. 2,890,4866/1959 6 2,936,674 5/1960 [22] Filed: Mar. 5, 1970 3 297 422 H1967 21Appl. No.: 16,664 3,460,928 8/1969 Related US. Application Data PrimaryExaminer Miga Attomey-Frank C. Parker and Bernard D. Bogdon [63]Continuation-in-part of Ser. No. 661,608, Aug. 18,

1967, abandoned, and a continuation-in-part of Ser. [57] ABSTRACT 1969abandoned' A method of manufacture of molds for casting finishedmultifocal plastic ophthalmic lenses of the type wherein the cor- [52]U.S. Cl ..65/3l, 65/37, 65/38, factions for the near field of vision areprovided on the convex 65/374 264/1 surface of the finished lens. [51]Int. Cl. ..C03c 15/00, C03b 1 H08, C03b [58] Field of Search ..65/37,38, 374, 31; 264/1 9 Claims, 31 Drawing Figures PATENTEDMAR 141912 SHEET1 BF 4 GHARLES H. ROSENBAUER INVENTOR.

i m-J PATENTEBHAR 14 I972 SHEET 2 OF 4 FIG.

FIG. I!

FIG. IO

CHARLE$ H. ROSENBAUER INVENTOR.

JQQ-AJ ATTORIVEY PATENTEDMAR 14 I972 sum 3 [IF 4 FIG.I9 I

F|G.24 CHARLES H. ROSENBAUER INVENTOR.

BY FRANK c. PARKER BERNARD D. BOGDON A TTORZVEIS PAIENTEDMAR 14 1972SHEET 4 BF 4 PIC-3.28

FIG.29

CHARLES H. ROSENBAUER INVENTOR.

BY FRANK c. PARKER BERNARD D. BOGDON ATTORNEYS MANUFACTURE OF MULTIFOCALOPHTHALMIC LENS MOLDS C ROSS-REF ERENCES TO RELATED APPLICATION Thisapplication is a continuation-in-part of my copending application, Ser.No. 661,608, filed Aug. 18, 1967 now abandoned and a furthercontinuation-in-part of my copending application, Ser. No. 820,582,filed Apr. 30, 1969 now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to improved methods of making molds for casting multifocalophthalmic lenses and to improved molds resulting from the aforesaidmethod.

2. Brief Description of the Prior Art The use of plastic ophthalmiclenses has been increasing because plastic lens blanks can be cast withone or both surfaces finished to the desired curvature. However, plasticlen ses are usually cast with only one finished surface and theprescription curve is subsequently applied to the other surface.

Cast plastic lenses are particularly advantageous for multifocal usewhere different curvatures are applied to one surface of the lens.Casting of multifocal lenses in properly manufactured molds can yieldlenses of precise curvature and configuration. However, in the past,production of casting molds has been difficult because of the multiplecurves and configurations and the close dimensional control required.

One method of making molds for casting plastic ophthalmic lenses isdisclosed in U.S. Pat. No. 3,297,422, issued to Stanley A. Emerson andGeorge A. Beasley on Jan. 10, 1967. However, practice of the inventiondisclosed in the Emerson et al., patent presents serious difficulties.One problem exists in the integrity of the separation line which extendsbetween different focal surfaces. It has been my experience that whengrinding and polishing glass molds it is extremely difficult to grindover a sharp edge or corner without chipping or faulting the area beingground. It is necessary to maintain a sharp segment line between thedistance and near vision segments of a multifocal lens and any chips,cracks or imperfections in the mold will produce a defective lens.

In addition, in the Emerson et al., patent the disclosed method ofcontrolling the outline size and shape of the near field of visioncomplementary curvature on the lens mold necessitates precise andgenerally time consuming control techniques, particularly during thegrinding operation of the surface defining a curvature complementary tothe curvature of the distance field of vision ofa lens. When thecomplementary distance curvature is being ground, grinding transpiresimmediately juxtaposed the surface of the mold defining thecomplementary near curvature thereby establishing at least part of theboundary between the surfaces having the complementary near and distancecurvatures and specifically, all of the outline of the complementarynear surface except for the separation line. According to this practice,the particular size and shape of the complementary near curvature isdifficult to generate because in that phase of the mold-making operationno specific visible finite mark or indicator is available as a controlpoint or level at which the grinding can be halted, presenting aparticularly tedious hand grinding operation. A hand grinding operationis usually necessary because of the generally uncontrollable multitudeof independent variables including the mold thickness, the fused segmentthickness and the wear of the grinding tool.

SUMMARY OF THE INVENTION To eliminate the above-described problems andto, in general, facilitate the manufacture of high-quality molds, l havedevised a method to maintain the integrity of the parting line betweenthe distance and near vision surfaces of the mold by adhering, forexample, by fusing a fused segment forming, for example, a circular disccomprising two or more sections LII fused together to a concave surfaceof a glass mold. The segment comprises either a first section comprisinggenerally less than a half circle of glass similar in composition to theglass of the mold blank and a second section of glass comprisinggenerally a section to complete a full circle with the first which iscapable of being etched away without attacking the mold or a two-partsegment comprising an outer segment section formed of a glass similar incomposition to the glass of the mold blank and an inner segment sectionsurrounded by the outer section formed of a glass which is etchable.

After fusing, the method comprises the steps of grinding and polishingthe mold including the fused segment to a predetermined complementarydistance curvature and then etching away either the selected secondsection or inner section of the segment thereby producing a finishedlens mold with a prescribed near vision cavity. As a result of this newand novel technique, plastic lens molds with a sharp segment line can beproduced with a minimum of difficulty in grinding.

For precisely controlling the outline shape and size of the mold surfacedefining the complementary near curvature, without the difficultiesexperienced following the prior art methods, it is preferred that thefusible segment comprise inner and outer segment sections ashereinbefore described. The inner section is formed in a preselectedshape and size and the outer segment section is formed to mate with itabout its lateral periphery. It should be appreciated that anypreselected shape is attainable even without using an etchable innersegment section provided the surrounding or outer segment section isformed to define an opening of selected outline shape and size.

The segment comprising, either the outer and inner segment sections, oronly the outer segment is adhered, for example, by fusing, to theconcave surface on the mold defining the complementary near curvature,as hereinbefore described. Once the last-mentioned step is accomplishedthe total boundary of the complementary near surface on the mold blankhas been defined and further, has been defined totally independent ofany grinding operation to follow. The subsequent grinding and polishingoperations form the mold surface having a curvature complementary to thecurvature of the distance field ofvision of the lens and bring, asdesired, the complementary near and distance surfaces of the moldrelatively close together. Care is taken, however, not to merge or havethe complementary near and distance surfaces intersect at more than asingle point, in order not to distort the preselected outline for themold surface having the curvature complementary to the curvature for thenear field of vision of the lens.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the concavehalf of a lens mold showing a recessed surface having a curvaturecomplementary to the near vision curvature of a lens;

FIG. 2 is a cross-sectional view of the lens mold along the plane ofline AA of FIG. 1 showing the complementary near vision curvature;

FIG. 3 is a perspective view of the lens mold and one type of fused twopart segment prior to fusion of the two part segment to the mold;

FIG. 3A is a perspective view of the lens mold and another type of fusedtwo part segment prior to fusion, the fused two part segment having aninner segment of a shape normally referred to as Panoptic;

FIG. 4 is a cross-sectional view of the lens mold and either the firstor second segment after fusion;

FIG. 5 is a cross-sectional view of the lens mold of FIG. 4 aftergrinding and polishing of a surface defining a curvature complementaryto a distance vision curvature of the lens;

FIG. 6 is a cross-sectional view of the lens mold of FIG. 5 afteretching;

FIG. 7 is a side elevational and cross-sectional view, partiallydiagrammatic, illustrating one form of lens mold assembly for use inmolding a plastic lens with, for example the lens mold of FIG. 6;

FIG. 8 is a cross-sectional view similar to FIG. of a lens mold halfprior to grinding of an intermediate surface having a curvaturecomplementary to the curvature of an intermediate field of vision in alens;

FIG. 9 is a cross-sectional view of the lens mold of FIG. 8 showing thecomplementary intermediate vision curvature;

FIG. 10 is a cross-sectional view of the lens mold of FIG. 9 afterfusion of a second two part segment;

FIG. 11 is a cross-sectional view of the lens mold of FIG. 10 aftergrinding of a surface defining a curvature complementary to a distancevision curvature of the lens;

FIG. 12 is a cross-sectional view of the lens mold of FIG. 11 afteretching;

FIG. 13 is a perspective view of an exemplary molded plastic lensshowing the multifocal surfaces manufactured using the mold of, forexample, FIG. 6;

FIG. 14 is a perspective view of an exemplary molded trifocal plasticlens manufactured using the mold of FIG. 12.

FIG. 15 is a perspective view of a molded fusible segment defining, forexample, an opening, having a shape generally referred to as Panoptic;

FIG. 16 is a cross-sectional view of the segment of F I6. 15 taken alongthe plane ofline 1616 in FIG. 15;

FIG. 17 is a cross-sectional view of the segment of FIG. 16 having aconvex surface formed thereon;

FIG. 18 is a cross-sectional view of the segment as shown in FIG. I7,fused to, for example, the lens mold of FIGS. 1 and 2, at the surfacedefining the curvature complementary to the curvature of the near fieldof vision of the lens;

FIG. 19 is a cross-sectional view of the lens mold of FIG. 18 after thegrinding of a surface defining the curvature complementary to thecurvature of the distance field of vision of the lens;

FIG. 20 is a perspective view of an outer segment section similar tothat shown in FIG. 15 further including an inner segment section inexploded view, formed, for example, in a shape generally referred to asPanoptic, for fusible matable engagement with the compatible openingdefined by the outer segment section;

FIG. 21 is a cross-sectional view of the outer segment section of FIG.20 along the plane ofline 21-2l ofFIG. 20;

FIG. 22 is a sectional view of a modified outer segment section of FIG.21 or alternate embodiment similar to the sectional view of the segmentin FIG. 16;

FIG. 23 is a sectional view of the outer segment section of FIG. 21along the plane ofline 2121 of FIG. 20 in fusible engagement with theinner segment section of FIG. 20;

FIG. 24 is the fused two part segment of FIG. 23 comprising inner andouter segment sections and defining on one end of the two part segment aconvex surface;

FIG. 25 is a cross-sectional view of the fused two part segment of FIG.24 and a lens mold blank of, for example, FIGS. 1 or 2 in fusedengagement at the convex surface of the two part segment and the surfacehaving a curvature complementary to the near vision curvature of thelens;

FIG. 26 is a cross-sectional view of the fused two part segment and moldblank of FIG. 25 after grinding to form a surface having a curvaturecomplementary to the distance vision curvature of the lens;

FIG. 27 is a plan view of the lens mold of FIG. 26 after etching of theremaining inner segment section, defining a surface having a curvaturecomplementary to the curvature of the distance field of vision whichcompletely surrounds the periphery of a recessed surface having a shapegenerally referred to as Panoptic, the recessed surface having acurvature complementary to the curvature of the near field of vision;

FIG. 28 is a cross-sectional view of the lens mold of FIG. 27 as viewedalong the plane of line 28-28 of FIG. 27;

FIG. 29 is a cross-sectional view of the lens mold of FIG. 27 along theplane of line 2929 of FIG. 27; and

FIG. 30 is a perspective view of a molded lens having a convex surfacedefining the curvature for the distance field of vision surrounding theperiphery of a convex surface defining the curvature for the near fieldof vision.

DESCRIPTION OF PREFERRED EMBODIMENTS A concave mold half for molding aplastic multifocal lens is shown generally by numeral 10 in FIG. 1. Acavity 14 of selected curvature 16, as best seen in FIG. 2, is generatedin surface 12 to provide the required near vision correction, bygrinding and polishing, in the mold half 10 at the proper position inorder to provide precise location of the near vision correction in thefinished lens. Concurrently with preparation of the mold half a segmentshown generally as 18 in FIG. 3 or 3A is prepared. This segment 18, asviewed in FIG. 3, is composed of a bottom portion 20 of a glasscomposition capable of being etched without attacking the glass used forthe mold 10, as will be hereinafter more fully described. The bottomportion 20 of the segment 18 is fused to a top portion 22 of the segment18 along a surface 24. It will be appreciated that the surface 24 may bea plane or curved surface. In FIG. 3A the two part segmen! 18 comprisesan outer portion 22A and an inner portion 20A which is of any desiredshape (the shape illustrated being commonly referred to as Panoptic) andwhich is fused within the outer portion 22A. The top portion 22 or outerportion 22A of the segments are of a glass composition preferablyidentical with that of the mold half 10.

After fusion of the two parts of the segment 18, as viewed in FIG. 3,the back surface 26 of the fused segment 18 is ground and polished to acurvature substantially identical with that of the surface 14 providedin the mold 10. Generally, the convex segment surface is not ground todefine a curvature which is exactly complementary to the substantiallycomplementary near surface on the lens mold because of manufacturingproblems involving captured air bubbles and improper fusion when thesegment is adhered to the mold blank. The selected radius of the groundconvex surface is generally less than the radius of the exactcomplementary curvature to preclude the mentioned problems. The groundand polished segment 18 is then fused to mold 10 as shown in FIG. 4.

After fusion, the mold 10 and segment 18 are ground and polished to thedesired radius of curvature to provide a curvature complementary to thecurvature of the distance field over surface 12 of mold 10, as shown inFIG. 5. Referring to FIG. 5 it can be seen that at this stage orpreparation there is a smooth mold 10 with the preselected complementarynear vision correction cavity filled with a glass 20 or 20A for etching.The entire mold is then subjected to an etching treatment, as willhereinafter be more fully described, in order to remove the glass 20 or20A leaving a completed mold half 10 with a complementary near visioncorrection cavity 28 with a straight sharp segment line 30, as best seenin FIG. 6, or with a shaped outline such as the one hereinbeforereferred to as Panoptic, as more fully described hereinafter. It isdesirable to dispose the segment line 30 at a slight angle to the axisof the mold to facilitate removal of a molded lens from the lens mold.The lens mold 10, as shown in FIG. 6, is then ready for molding of theplastic multifocal lenses.

In order to mold the plastic lens a second mold half 32, as shown inFIG. 7, is prepared with a ground and polished convex surface 34. Thesurface 34 can be finished to a desired prescription curvature or alesser curvature to allow for subsequent finishing to a variety ofprescriptions. The mold halves l0 and 32 are then assembled into aspaced relationship, as shown in FIG. 7, and held apart by suitablemeans such as a ring 36 with an inwardly projecting rib 38 and held witha spring clamp 40. For simplicity only one clamp 40 is shown, however,it is understood that several may be used. The liquid plastic monomer isintroduced into the mold assembly as at inlet 42, shown in FIG. 7. Thelens blanks may be made of any of the known optical plastic materials,for example, polymerized methyl methacrylate resin or polymerized methyldiethylene glycol di (allyl carbonate).

The optical plastic material 44 is introduced into the mold cavity atinlet 42 until the mold cavity is filled. The entire assembly is thensubjected to the proper hardening and/or curing cycle as dictated by theoptical plastic material. When the hardening and/or curing cycle iscomplete the molds 10 and 32 are removed from the plastic lens blank.

It must be remembered that during the preparation of the mold halves,assembly of said halves into the mold, casting of the lens, andhardening and/or curing, the mold surfaces must be kept clean and freefrom all foreign matter such as lint, dust, dirt, etc., in order toyield plastic lenses of the desired optical properties. A completed lensblank 46 molded by the above process is shown in FIG. 13. The lens blank46 contains the preselected near vision correction segment 48, thesurface of which has the curvature 16 molded by the surface 14 of thelens mold and the distance vision surface 50 molded by surface 12 ofthelens mold 10.

The above-described mold is used for molding the indicated type ofbifocal lens surface. It is to be understood that by varying the contourof the surface 14 of the lens mold l0 and correspondingly, the shape ofsegment 18, the resulting location and shape of the near visioncorrection portion of the finished lens may be selectively located andmade to any desired configuration.

In view of the above description it can be shown that my method isapplicable to the making of molds for casting trifocal lenses. Referringto FIGS. 8 through 12 a suitable concave mold blank 10 is preparedexcept for grinding and polishing of the distance vision portion and forremoval of the preferential etching glass 20. The mold blank 10 is thenprovided with another recess of intermediate radius of curvature 54, theradius ofcurvature 54 being between that of the radius of the curvatureof surface 12 and surface 14. The location of the center line ofcurvature 54 should be slightly below the optical center of the lensmold l0 and above the optical center of surface 14'. Concurrentlyanother two part segment 18, as shown on FIG. 10 composed ofa bottomportion 20 of preferential etching glass and a top portion 22 of glassidentical in composition to that of mold 10 is prepared by fusion of thetwo parts. The back surface of segment 18 is ground and polishedsubstantially to a curvature identical to that of sur face 54 ashereinbefore described. The segment 54 thus suitably prepared is fusedto the mold blank 10.

After fusion the mold blank 10' and the two part segment 18 are groundand polished to form the complementary curvature to the curvature of thedistance field of vision on the mold blank 10. The entire mold 10' isthen subjected to an etching treatment whereby glass 20 and 20' beingsimilar are etched away leaving a lens mold of three radii of curvature,namely 12, 54, and 14. The mold 10 can then be assembled into a castingfixture as was previously described in reference to FIG. 7 and a lensblank 58, as shown in FIG. 14, produced thereby. The lens blank 58contains a curved convex surface 60 to accommodate the distance field ofvision, a surface 62 to accommodate the intermediate field of vision anda surface 64 to accommodate the near field of vision.

Further understanding of the instant invention will be gained from thefollowing examples.

EXAMPLE I A 71 millimeter round mold blank of a glass composed of, byweight percent, 68.81 percent SiO 10.23 percent K 0, 1.00 percent A1 07.34 percent Na O, 7.82 percent CaO, 0.15 percent TiO 0.69 percent MnOand 3.96 percent CeO was prepared. A suitable concave curve was formedin the lens blank. The concave side of the mold was then countersunk inthe area below the center of mold for the desired near visioncorrection, in this case 2.00 diopter. A segment 31 millimeters indiameter was made with a bottom portion of a glass composed of, byweight percent, 31.74 percent SiO 2.86 percent K O, 18.63 percent 330,4.48 percent ZnO, 6.32 percent Na O, 5.54 percent TiO 7.02 percent ZrO1.53 percent CaO, 6.70 percent SrO, 8.12 percent La O 6.21 percent 8 00.60 percent A1 0 and 0.25 percent AS203 and a top portion of glasssimilar in composition to that of the mold half described above. Thesegment was fused with a plane surface between top and bottom glasses. Acurvature substantially matching that of the countersink on the moldhalf was ground and polished on the segment with the exception thatprism was introduced on this surface in order to incline thesegment-lens interface approximately 10 for easy release of the plasticlens from the mold. The blank and segment were then matched and fused,the segment parting line being 3.0 mm. below the optical center of thelens, suing well-known bifocal glass technology. Subsequent to fusionthe mold blank including the segment glass was ground and polished toform the complementary distance field on the mold half. The mold wasthen placed in a suitable container and covered with a 20 percentsolution of 37 percent hydrochloric acid and the container placed in anultrasonic generator for 3 hours. Periodic inspection was performed andwhen the preferential etching glass was dissolved (approximately 3hours) the lens mold was removed from the acid solution and rinsed inclear water. Inspection of the mold revealed a multicolored film in thecavity of the mold which was dissolved in a 1.6 percent solution ofEspray" alkali cleaner a product of Wyandotte Chemical Company, .1. B.Ford Division, Wyandotte, Michigan. The finished mold was then rinsed inclean water and dried using an air blast. The other half of the mold wasprepared and several lenses of acceptable quality molded.

EXAMPLE II A 71 millimeter round concave mold glass blank composed of,by weight percent, 66.10 percent SiO 9.44 percent K 0, 8.96 percent NaO, 0.50 percent A1 0 0.50 percent A5 0 0.75 percent Sb O 2.62 percent FeO 0.09 percent C, 0.12 percent NiO, 0.01 percent C0 0,, and 10.91percent ZnO was prepared. A near vision connection cavity of -2.00diopters was prepared in the lower half of the mold section as inExample I above. A fused segment, the lower portion composed ofa glassof, by weight percent, 32.58 percent SiO 18.47 percent BaO, 4.73 percentZnO, 9.77 percent Na O, 1.25 percent K 0, 6.95 percent TiO 6.53 percentZnO 1.49 percent CaO, 8.77 percent PbO, 9.28 percent B 0 0.036 percentC0 0 and 0.144 percent MO and a top portion composed of a glass similarin composition to the mold glass was prepared. Fusion of the segment andgrinding were performed as in Example I. At this point the mold wasprovided with a l.00 diopter near vision correction cavity on a centerline above the initial 2.00 diopter cavity. Another segment composed ofa top half of mold glass and a bottom half of a composition similar tothe first segment bottom portion was prepared. A matching curve wasground and polished on this second segment corresponding to the 1.00diopter cavity. This second segment was fused to the mold as before;however, with the segment parting line 3 mm. below optical center of themold and above the parting line of the first segment. After fusion themold blank and segment were ground and polished to form thecomplementary distance curvature of the mold. The mold was placed in acontainer and covered with a 20 percent solution of 37 percent I-ICl andthe container placed in an ultrasonic generator. After 4 hours bothlower segment glasses were dissolved away leaving a film as before. Thefilm was removed as described in Example I. A suitable mating half ofthe mold was prepared and several lenses molded. The lenses thus moldedwere found to be acceptable with +1.00 and +2.00 diopter corrections,for intermediate and near vision.

In FIG. 15 there is illustrated a fusible segment similar inconstruction to the outer portion 22 A of the two part segment 18illustrated in FIG. 3A. The application of only an outer segmentportion, such as segment 80, without an inner segment of mating size andconfiguration was hereinbefore briefly discussed. As desired the segment80 is provided with an opening the outline of which defines a selectedsize and shape. The opening outline thereby provides for defining thefinal shape and size of the boundary of a surface on the mold blank,such as the surface defined by the cavity 14, which has a curvaturecomplementary to the curvature of a selected near field of vision for alens.

The segment 80 generally is formed as a circular flat sided disc and inconfiguration generally resembles a lateral section cut from a cylinder.The disc segment 80, as illustrated in FIG. 15, defines an opening 82having a lateral inner wall extending in the direction of the axis ofthe disc, shaped in a configuration which is generally referred to asPanoptic. The location of the defined opening is preselected and isdisposed to provide the best lens surface location for a particularuser.

IN FIG. 16, a cross-sectional view of the segment 80 is provided and itwill be appreciated from this view that the ends 84 and 86 of thecylindrical disc are substantially planar and parallel. Subsequently, agrinding operation is performed on, for example, the surface 86 togenerate a convex surface 88, as best seen in FIG. 17, having acurvature which is substantially complementary to, for example, thecurvature of the near field of vision cavity 14, illustrated in FIG. 1.As hereinbefore described the length of the radius used to generate thesurface 88 is slightly less than the length of the radius used togenerate the surface 14 in order to facilitate fusing techniques and topreclude problems arising from the formation of air bubbles or pooradhesion at the fused surfaces.

In FIG. 18, the segment 80 has been fused to the mold blank 10, matinglyengaging substantially complementary surfaces 88 and 14. In a subsequentstep, a surface 90 is generated to define a curvature complementary tocurvature of the selected distance field of vision for the lens. Thecurvature of the surface 90 is defined in FIG. 18 by the broken line B-Bwhich in the cross sectional view of FIG. 18 extends through a point X.The point X is defined as a particular point of intersection ofahereinafter defined line in the lateral wall surface defining the shapedopening, for example, the opening having a shape referred to asPanoptic. The line is defined as extending parallel to the axis of thedisc segment 80 and is disposed in the inner wall surface at thatlocation in the inner surface which is least distant from the outerlateral axially extending peripheral surface 91 of the disc segment 80.Point X lies at the intersection of the defined line and the curvedsurface having a curvature complementary to the curvature of theselected near field of vision, such as the surface defined by the cavity14. It will be appreciated that the intersection is at one terminus ofthe defined line.

As seen in FIG. 19, point X, as defined, is a point on the line BB whichdefines the curvature complementary to the curvature of the selecteddistance field of vision. It will be appreciated that in operation, thegrinding and polishing of the complementary distance curvature may bestopped before the grinding tool penetrates to the locus of point X ormay be continued up to the point X. If grinding is permitted to proceedinto the lens mold past the point X the outline shape of thecomplementary near field will be distorted from the selected and desiredshape. In this exemplary case, the selected shape referred to asPanoptic will be violated.

It will be appreciated that in the art of making molds for lenses that amajority of the operations, particularly the grinding operations, arehand operations in which the expertise of the craftsmen is greatlydepended upon. In the grinding of the surface having a curvaturecomplementary to the curvature of the distance field of vision in thelens, the expertise of the craftsmen is relied upon not to operate thegrinding tool beyond the X point, as hereinbefore defined. One advantageof the present invention over the prior art is that the grinding tooloperator has a visible boundary defined by the outline of the shapedopening to which to grind.

In the FIGURE sequence 20-26 essentially the same process ashereinbefore mentioned relating to the illustrations -19 is followedexcept for the fact that there is included in the discussion of FIGS.-26 the application of an etchable inner segment section 92, illustratedin a shape referred to as Panoptic. The segment section 92 mateablyengages with a compatible opening 94 defined in a generally circularlyformed fiat sided carrier disc 96, also referred to as an outer segmentsection.

The carrier disc 96 is, as is the segment 80, formed of a materialsimilar, but preferably identical, in composition to, for example, theglass used to form the mold blank 10. The

inner segment section 92 is formed of an etchable glass such as thathereinbefore mentioned for use in forming the bottom portion 20 and theinner segment section 20A of FIGS. 3 and 3A, respectively.

In FIGS. 21 and 22 there are illustrated alternate embodiments 96 and96", respectively, of the outer segment section 96. Each is shown incross-sectional view to illustrate in one, the shaped opening 94 and abottom surface 95 defined by the segment section 96', as best seen inFIG. 21, and in the other, no bottom but the opening 94 passing clearthrough the outer section 96" from one flat side to the other, as bestseen in FIG. 22. It will be appreciated that either embodiment 96' or96" of the outer segment section 96 is for carrying and mating with theinner segment section 92 and being fused therewith. In use, the segmentsection 96', illustrated in FIG. 21, is fused to the inner segmentsection 92 at the bottom surface 95, thereby supporting the section 92and facilitating the fusing of the lateral side of the segment section92 to the inner wall of the outer segment section 96.

FIG. 23 illustrates, in cross section, the inner segment section 92fused to the outer segment section 96' in preparation for generation ofa convex surface 98, as seen in FIG. 24, having a curvaturesubstantially complementary to the curvature of the near vision cavity14 of FIG. 1.

The immediately succeeding manufacturing step comprises fusing the fusedtwo part segment comprising section 96' to matingly engage its convexsurface 98 with the surface of the concave cavity 14 as shown in FIG.25. A generating or grinding tool is then provided to grind the two partsegment and the concave surface 12 of the lens mold 10 substantially toa curvature defined by the line C-C, illustrated in FIG. 25, to therebyprovide a surface 100 having a curvature complementary to the curvatureof the selected distance field of vision for the lens. As hereinbeforementioned, particularly regarding FIG. 19, generation of the surface 100is similarly accomplished without passing the grinding tool through thepoint X of FIG. 25. Point X is defined in a manner similar to the methodof definition of point X of FIGS. 18 and 19.

After etching of a portion 99 of glass of the inner segment section 92which remains after the preceding mentioned grinding operation, a mold101 is provided for use in molding a bifocal lens and comprisescomplementary distance vision surface 102 and complementary near visionsurface 104, as best seen in the plan view of FIG. 27. As illustrated,the surface 102 completely surrounds the periphery of the surface 104and the surfaces 102 and 104 share one common point X", as best seen inthe cross-sectional view in FIG. 28.

As hereinbefore mentioned the surfaces 102 and 104 are generated toshare no more than one common point. For clarity the cross sectionalview of FIG. 29 is provided to illustrate that generally a substantiallylateral wall exists between the complementary distance vision andcomplementary near vision surfaces 102 and 104, respectively. Ashereinbefore described it may be advantageous to include prism or draftin the lateral wall extending between the surfaces 102 and 104 in orderto facilitate manufacturing techniques.

FIG. 30 illustrates a completed lens 106 having surfaces 104' and 104'of different focal length with a substantially vertical wall of varyingheight extending between the surface. It will be appreciated that thewall height may diminish to no measurable height at one point, but onlyif at the time of generation in the lens mold 101 of the surface 102having a curvature complementary to the curvature of the distance fieldof vision of the lens, the generating tool penetrates to the locus ofthe defined, for example, point X".

From the foregoing it is evident that I have provided an improved methodof making molds for the production of multifocal ophthalmic lenses andlens blanks whereby the production of the molds with a surfacecontaining multiple curvatures can be produced in a simplified mannerand to precise tolerances. It is further evident that the mold producedby my improved method contains multiple curves and configurationscontrolled to precise tolerance levels.

While I have used the term molding in describing the making of lensesand lens blanks by my process I intend to encompass the term casting bywhich term the molding process is sometimes referred.

Although only certain forms of the present invention are shown anddescribed herein in detail other forms are possible and changes may bemade without departing from the spirit and scope of the invention asdefined in the following claims.

I claim:

1. A method of making a mold face for molding an ophthalmic lensdefining multifocal first and second ophthalmic surfaces, eachophthalmic surface of the lens being of predetermined curvature fordiffering fields of vision, the first ophthalmic surface of the lenshaving a peripheral outline configuration which is other than completelycircular, the outline configuration defining a portion ofa continuouslens wall extending from the first ophthalmic surface of the lens to thesecond ophthalmic surface of the lens, wherein the mold face has firstand second concave mold surfaces and a continuous mold wall extendingfrom the second mold surface to intersect the first mold surface at acontinuous line for defining the other than completely circularperipheral outline configuration of the first ophthalmic surface of thelens, each concave mold surface having a curvature identical to thepredetermined curvature of each, respective, multifocal first and secondophthalmic surface ofthe lens, comprising the steps of:

forming a mold blank;

grinding and polishing the mold blank to a curvature identical to thefirst predetermined curvature of one field of vision for the lens tothereby form the first concave mold surface on the mold blank; forming ahole shaped segment ofa first material to define a hole by forming acontinuous inner mold wall having the other than completely circularoutline configuration;

forming a filler section of a material different than the material ofthe hole-shaped segment to define a continuous outer wall ofsubstantially the same configuration and size as the formed continuousinner mold wall of the holeshaped segment;

forming a disc by adhering the filler section at its continuous outerwall to the hole-shaped segment at its continuous inner mold wall;

grinding and polishing a convex surface on the formed disc to acurvature identical to the curvature of the first concave mold surfaceground and polished on the mold blank;

adhering the disc at the ground and polished convex surface of the discto the mold blank at the first concave mold surface;

grinding and polishing the combined mold blank and disc to a curvatureidentical to the second predetermined curvature of another field ofvision for the lens by grinding and polishing so as not to intersect thecontinuous line defined by the intersection of the continuous mold wallwith the first concave mold surface on the mold blank, the continuousline being defined after the adhering of the convex surface of theground and polished disc to the mold blank, the grinding and polishingof the mold blank and the disc thereby forming the second concave moldsurface on the mold blank; and

removing the filler section from the combined disc and mold blank toexpose the first concave mold surface to thereby completely form themold face defining the first and second concave mold surfaces havingrespective curvatures identical to the predetermined curvatures for thelens for differing fields of vision, the formed continuous inner moldwall extending between the first and second concave mold surfaces andintersecting the first mold surface at the continuous line for definingthe other than completely circular peripheral outline configuration ofthe first ophthalmic surface of the lens.

2. The method of making a mold face as defined in claim 1, wherein thedisc for adhering to the first concave mold surface of the mold blank isformed by fusing the hole shaped segment and the filler sectiontogether.

3. The method of making a mold face as defined in claim 1, wherein thedisc is adhered to the first concave mold surface of the mold blank byfusing.

4. The method of making a mold face as defined in claim 1, wherein thefiller section is removed by chemically attacking its materialcomposition.

5. The method of making a mold face as defined in claim 1, wherein thefiller section is removed by mechanically and chemically attacking itsmaterial composition.

6. The method of making a mold face as defined in claim 1, wherein thecontinuous mold wall is formed to define a D- shaped curve.

7. A method of making a mold face for molding an ophthalmic lensdefining multifocal first and second ophthalmic surfaces, eachophthalmic surface of the lens being of predetermined curvature fordiffering fields of vision, the first ophthalmic surface of the lenshaving a boundary outline configuration which is other than completelycircular, the outline configuration defining a portion of a continuouslens wall extending from the first ophthalmic surface of the lens to thesecond ophthalmic surface of the lens, wherein the mold face has firstand second concave mold surfaces and a continuous mold wall extendingfrom the second mold surface to intersect the first mold surface at acontinuous line for defining the other than completely circular boundaryoutline configuration of the first ophthalmic surface of the lens, eachconcave mold surface having a curvature identical to the predeterminedcurvature of each, respective, multifocal first and second ophthalmicsurface ofthe lens, comprising the steps of:

forming a mold blank;

grinding and polishing the mold blank to a curvature identical to thefirst predetermined curvature of one field of vision for the lens tothereby form the first concave mold surface on the mold blank;

forming a hole shaped disc to define a hole by forming a continuousinner mold wall having the other than completely circular boundaryoutline at least at one portion of the inner mold wall;

grinding and polishing a convex surface on the formed disc to acurvature identical to the curvature of the first concave mold surfaceground and polished on the mold blank;

adhering the disc at the ground and polished convex surface of the discto the mold blank at the first concave mold surface; and

grinding and polishing the combined mold blank and disc to a curvatureidentical to the second predetermined curvature of another field ofvision for the lens to provide the second concave mold surface as onecontinuous uniform concave surface comprising the disc and the moldblank by grinding and polishing in order that no point on the secondconcave mold surface is common with any point on the first concave moldsurface, to thereby completely form the mold face with the first concavemold surface set apart from the second concave mold surface by thecontinuous mold wall extending from the second concave mold surface tointersect the first concave mold surface at the continuous line fordefining the other than completely circular boundary outline of thefirst ophthalmic surface of the lens.

8. The method of making the mold face as defined in claim 7, whereingrinding and polishing the second concave mold surface in the disc andthe mold blank to the curvature identical to the second predeterminedophthalmic curvature of said another field of vision for the lens,further comprises:

grinding and polishing the second concave mold surface to a surfacelevel whereat substantially only one point on the first concave moldsurface, that point disposed at the continuous line for defining theother than completely circular boundary outline of the first ophthalmicsurface of the lens, comprises a point on the second concave surface.

9. A method of making a mold face for molding an ophthalmic lensdefining multifocal first, second, and third ophthalmic surfaces, eachophthalmic surface of the lens being of predetermined curvature fordiffering fields of vision, the first ophthalmic surface of the lenshaving a peripheral outline configuration which is other than completelycircular, the outline configuration defining a portion of a continuouslens wall ex tending at least in part from the first ophthalmic surfaceof the lens to the second ophthalmic surface of the lens and extendingat least in part to the third ophthalmic surface of the lens, the secondophthalmic surface of the lens having a peripheral outline configurationwhich is other than completely circular defining a portion of thecontinuous wall extending at least in part from the second ophthalmicsurface of the lens to the third ophthalmic surface of the lens, whereinthe mold face has first, second and third concave mold surfaces and acontinuous mold wall extending from the third mold surface to intersectthe first and second mold surfaces at portions of continuous lines fordefining the other than completely circular peripheral outlineconfigurations of the first and second ophthalmic surfaces of the lens,each concave mold surface having a curvature identical to thepredetermined curvature of each, respective, multifocal first, secondand third ophthalmic surface of the lens, comprising the steps of:

forming a mold blank;

grinding and polishing the mold blank to a curvature identical to thefirst predetermined curvature of one field of vision for the lens tothereby form the first concave mold surface on the mold blank;

forming a first hole-shaped segment of a first material to define a holeby forming a continuous inner mold wall having an other than completelycircular outline configuration;

forming a first filler section of a material different than the materialof the first hole-shaped segment to define a continuous outer wall ofsubstantially the same configuration and size as the formed continuousinner mold wall of the first hole-shaped segment;

forming a first disc by adhering the first filler section at itscontinuous outer wall to the first hole-shaped segment at its continuousinner mold wall;

grinding and polishing a convex surface on the formed first disc to acurvature identical to the curvature of the first concave mold surfaceground and polished on the mold blank;

adhering the first disc at the ground and polished convex surface of thefirst disc to the mold blank at the first concave mold surface;

grinding and polishing the combined mold blank and first disc to acurvature identical to the second predetermined curvature of anotherfield of vision for the lens by grinding and polishing so as not tointersect the continuous line defined by the intersection of thecontinuous mold wall of the first hole shaped segment with the firstconcave mold surface on the mold blank, the continuous tine beingdefined after the adhering of the convex surface of the ground andpolished first disc to the mold blank at the first concave mold surface,the grinding and polishing of the mold blank and the first disc therebyforming the second concave mold surface on the combined mold blank andfirst disc;

forming a second hole-shaped segment of the first material to define ahole by forming a continuous inner mold wall having an other thancompletely circular outline configuration;

forming a second filler section of a material different than thematerial of the second hole-shaped segment to define a continuous outerwall of substantially the same configuration and size as the formedcontinuous inner mold wall of the second hole-shaped segment;

forming a second disc by adhering the second filler section at itscontinuous outer wall to the second hole-shaped se cut at its continuousinner mold wall; grin mg and polishing a convex surface on the formedsecond disc to a curvature identical to the curvature of the secondconcave mold surface ground and polished on the mold blank and firstdisc;

adhering the second disc at the ground and polished convex surface ofthe second disc to the mold blank at the second concave mold surface;

grinding and polishing the combined mold blank and first and seconddiscs to a curvature identical to the third predetermined curvature ofanother field of vision for the lens by grinding and polishing so as notto intersect the continuous line defined by the intersection of thecontinuous mold wall of the second hole-shaped segment with the secondconcave mold surface on the mold blank, the continuous line beingdefined after the adhering of the convex surface of the ground andpolished second disc to the mold blank at the second concave moldsurface, the grinding and polishing of the mold blank and the first andsecond discs thereby fonning the third concave mold surface on the moldblank; and

removing the first and second filler sections from the combined firstand second discs and mold blank to expose the first and second concavemold surfaces to thereby completely form the mold face defining thefirst, second and third concave mold surfaces having respectivecurvatures identical to the predetermined curvatures for the lens fordiffering fields of vision, the formed continuous inner mold wallsextending between the first, second and third concave mold surfaces andintersecting the first and second mold surfaces at the respectivecontinuous lines for defining the other than completely circularperipheral outline configurations of the first and second ophthalmicsurfaces of the lens,

1. A method of making a mold face for molding an ophthalmic lensdefining multifocal first and second ophthalmic surfaces, eachophthalmic surface of the lens being of predetermined curvature fordiffering fields of vision, the first ophthalmic surface of the lenshaving a peripheral outline configuration which is other than completelycircular, the outline configuration defining a portion of a continuouslens wall extending from the first ophthalmic surface of the lens to thesecond ophthalmic surface of the lens, wherein the mold face has firstand second concave mold surfaces and a continuous mold wall extendingfrom the second mold surface to intersect the first mold surface at acontinuous line for defining the other than completely circularperipheral outline configuration of the first ophthalmic surface of thelens, each concave mold surface having a curvature identical to thepredetermined curvature of each, respective, multifocal first and secondophthalmic surface of the lens, comprising the steps of: forming a moldblank; grinding and polishing the mold blank to a curvature identical tothe first predetermined curvature of one field of vision for the lens tothereby form the first concave mold surface on the mold blank; forming ahole shaped segment of a first material to define a hole by forming acontinuous inner mold wall having the other than completely circularoutline configuration; forming a filler section of a material differentthan the material of the hole-shaped segment to define a continuousouter wall of substantially the same configuration and size as theformed continuous inner mold wall of the hole-shaped segment; forming adisc by adhering the filler section at its continuous outer wall to thehole-shaped segment at its continuous inner mold wall; grinding andpolishing a convex surface on the formed disc to a curvature identicalto the curvature of the first concave mold surface ground and polishedon the mold blank; adhering the disc at the ground and polished convexsurface of the disc to the mold blank at the first concave mold surface;grinding and polishing the combined mold blank and disc to a curvatureidentical to the second predetermined curvature of another field ofvision for the lens by grinding and polishing so as not to intersect thecontinuous line defined by the intersection of the continuous mold wallwith the first concave mold surface on the mold blank, the continuousline being defined after the adhering of the convex surface of theground and polished disc to the mold blank, the grinding and polishingof the mold blank and the disc thereby forming the second concave moldsurface on the mold blank; and removing the filler section from thecombined disc and mold blank to expose the first concave mold surface tothereby completely form the mold face defining the first and secondconcave mold surfaces having respective curvatures identical to thepredetermined curvatures for the lens for differing fields of vision,the formed continuous inner mold wall extending between the first andsecond concave mold surfaces and intersecting the first mold surface atthe continuous line for defining the other than completely circularperipheral outline configuration of the first ophthalmic surface of thelens.
 2. The method of making a mold face as defined in claim 1, whereinthe disc for adhering to the first concave mold surface of the moldblank is formed by fusing the hole shaped segment and the filler sectiontogether.
 3. The method of making a mold face as defined in claim 1,wherein the disc is adhered to the first concave mold surface of themold blank by fusing.
 4. The method of making a mold face as defined inclaim 1, wherein the filler section is removed by chemically attackingits material composition.
 5. The method of making a mold face as definedin claim 1, wherein the filler section is removed by mechanically andchemically attacking its material composition.
 6. The method of making amold face as defined in claim 1, wherein the continuous mold wall isformed to define a D-shaped curve.
 7. A method of making a mold face formolding an ophthalmic lens defining multifocal first and secondophthalmic surfaces, each ophthalmic surface of the lens being ofpredetermined curvature for differing fields of vision, the firstophthalmic surface of the lens having a boundary outline configurationwhich is other than completely circular, the outline configurationdefining a portion of a continuous lens wall extending from the firstophthalmic surface of the lens to the second ophthalmic surface of thelens, wherein the mold face has first and second concave mold surfacesand a continuous mold wall extending from the second mold surface tointersect the first mold surface at a continuous line for defining theother than completely circular boundary outline configuration of thefirst ophthalmic surface of the lens, each concave mold surface having acurvature identical to the predetermined curvature of each, respective,multifocal first and second ophthalmic surface of the lens, comprisingthe steps of: forming a mold blank; grinding and polishing the moldblank to a curvature identical to the first predetermined curvature ofone field of vision for the lens to thereby form the first concave moldsurface on the mold blank; forming a hole shaped disc to define a holeby forming a continuous inner mold wall having the other than completelycircular boundary outline at least at one portion of the inner moldwall; grinding and polishing a convex surface on the formed disc to acurvature identical to the curvature of the first concave mold surfaceground and polished on the mold blank; adhering the disc at the groundand polished convex surface of the disc to the mold blank at the firstconcave mold surface; and grinding and polishing the combined mold blankand disc to a curvature identical to the second predetermined curvatureof another field of vision for the lens to provide the second concavemold surface as one continuous uniform concave surface comprising thedisc and the mold blank by grinding and polishing in order that no pointon the second concave mold surface is common with any point on the firstconcave mold surface, to thereby completely form the mold face with thefirst concave mold surface set apart from the second concave moldsurface by the continuous mold wall extending from the second concavemold surface to intersect the first concave mold surface at thecontinuous line for defining the other than completely circular boundaryoutline of the first ophthalmic surface of the lens.
 8. The method ofmaking the mold face as defined in claim 7, wherein grinding andpolishing the second concave mold surface in the disc and the mold blankto the curvature identical to the second predetermined ophthalmiccurvature of said another field of vision for the lens, furthercomprises: grinding and polishing the second concave mold surface to asurface level whereat substantially only one point on the first concavemold surface, that point disposed at the continuous line for definingthe other than completely circular boundary outline of the firstophthalmic surface of the lens, comprises a point on the second concavesurface.
 9. A method of making a mold face for molding an ophthalmiclens defining multifocal first, second, and third ophthalmic surfaces,each ophthalmic surface of the lens being of predetermined curvature fordiffering fields of vision, the first ophthalmic surface of the lenshaving a peripheral outline configuration which is other than completelycircular, the outline configuration defining a portion of a continuouslens wall extending at least in part from the first ophthalmic surfaceof the lens to the second ophthalmic surface of the lens and extendingAt least in part to the third ophthalmic surface of the lens, the secondophthalmic surface of the lens having a peripheral outline configurationwhich is other than completely circular defining a portion of thecontinuous wall extending at least in part from the second ophthalmicsurface of the lens to the third ophthalmic surface of the lens, whereinthe mold face has first, second and third concave mold surfaces and acontinuous mold wall extending from the third mold surface to intersectthe first and second mold surfaces at portions of continuous lines fordefining the other than completely circular peripheral outlineconfigurations of the first and second ophthalmic surfaces of the lens,each concave mold surface having a curvature identical to thepredetermined curvature of each, respective, multifocal first, secondand third ophthalmic surface of the lens, comprising the steps of:forming a mold blank; grinding and polishing the mold blank to acurvature identical to the first predetermined curvature of one field ofvision for the lens to thereby form the first concave mold surface onthe mold blank; forming a first hole-shaped segment of a first materialto define a hole by forming a continuous inner mold wall having an otherthan completely circular outline configuration; forming a first fillersection of a material different than the material of the firsthole-shaped segment to define a continuous outer wall of substantiallythe same configuration and size as the formed continuous inner mold wallof the first hole-shaped segment; forming a first disc by adhering thefirst filler section at its continuous outer wall to the firsthole-shaped segment at its continuous inner mold wall; grinding andpolishing a convex surface on the formed first disc to a curvatureidentical to the curvature of the first concave mold surface ground andpolished on the mold blank; adhering the first disc at the ground andpolished convex surface of the first disc to the mold blank at the firstconcave mold surface; grinding and polishing the combined mold blank andfirst disc to a curvature identical to the second predeterminedcurvature of another field of vision for the lens by grinding andpolishing so as not to intersect the continuous line defined by theintersection of the continuous mold wall of the first hole shapedsegment with the first concave mold surface on the mold blank, thecontinuous line being defined after the adhering of the convex surfaceof the ground and polished first disc to the mold blank at the firstconcave mold surface, the grinding and polishing of the mold blank andthe first disc thereby forming the second concave mold surface on thecombined mold blank and first disc; forming a second hole-shaped segmentof the first material to define a hole by forming a continuous innermold wall having an other than completely circular outlineconfiguration; forming a second filler section of a material differentthan the material of the second hole-shaped segment to define acontinuous outer wall of substantially the same configuration and sizeas the formed continuous inner mold wall of the second hole-shapedsegment; forming a second disc by adhering the second filler section atits continuous outer wall to the second hole-shaped segment at itscontinuous inner mold wall; grinding and polishing a convex surface onthe formed second disc to a curvature identical to the curvature of thesecond concave mold surface ground and polished on the mold blank andfirst disc; adhering the second disc at the ground and polished convexsurface of the second disc to the mold blank at the second concave moldsurface; grinding and polishing the combined mold blank and first andsecond discs to a curvature identical to the third predeterminedcurvature of another field of vision for the lens by grinding andpolishing so as not to intersect the continuous line defined by theintersection of the continuous mOld wall of the second hole-shapedsegment with the second concave mold surface on the mold blank, thecontinuous line being defined after the adhering of the convex surfaceof the ground and polished second disc to the mold blank at the secondconcave mold surface, the grinding and polishing of the mold blank andthe first and second discs thereby forming the third concave moldsurface on the mold blank; and removing the first and second fillersections from the combined first and second discs and mold blank toexpose the first and second concave mold surfaces to thereby completelyform the mold face defining the first, second and third concave moldsurfaces having respective curvatures identical to the predeterminedcurvatures for the lens for differing fields of vision, the formedcontinuous inner mold walls extending between the first, second andthird concave mold surfaces and intersecting the first and second moldsurfaces at the respective continuous lines for defining the other thancompletely circular peripheral outline configurations of the first andsecond ophthalmic surfaces of the lens.